The book was published in the United Kingdom on 2 July 1998 by Bloomsbury and in the United States on 2 June 1999 by Scholastic Inc. Although Rowling found it difficult to finish the book, it won high praise and awards from critics, young readers and the book industry, although some critics thought the story was perhaps too frightening for younger children. Much like with other novels in the series, Harry Potter and the Chamber of Secretstriggered religious debates; some religious authorities have condemned its use of magical themes, while others have praised its emphasis on self-sacrifice and on the way in which a person's character is the result of the person's choices.

Several commentators have noted that personal identity is a strong theme in the book, and that it addresses issues of racism through the treatment of non-magical, non-human and non-living characters. Some commentators regard the diary as a warning against uncritical acceptance of information from sources whose motives and reliability cannot be checked. Institutional authority is portrayed as self-serving and incompetent. The book is also known to have some connections to the sixth novel of the series, Harry Potter and the Half-Blood Prince.

Harry spends another miserable summer with his only remaining family, the Dursleys. During a dinner party given by Harry's aunt and uncle, Dobby, a house-elf, pops into Harry's bedroom, warning him that if he returns to Hogwarts, terrible things will happen. Harry disregards it, and Dobby wreaks havoc in the kitchen, infuriating the Dursleys, who angrily imprison Harry. Harry is rescued by his friend Ron Weasley and brothers Fred and George in their flying car, spending the summer at the Weasley home. Harry accidentally ends up in Knockturn Alley, the dark arts section of Diagon Alley. Fortunately, he encounters his friend Hagrid, Hogwarts's gamekeeper, there to buy flesh-eating slug repellent, who guides him safely back into Diagon Alley to shop for school supplies.

In the company of the Weasleys, Harry encounters the famous Gilderoy Lockhart who informs everyone that he is the new Defense Against the Dark Arts teacher and demands to be in a photoshoot with Harry, revealing his enthusiasm for self-promotion. Soon after, the Weasleys depart with Harry for King's Cross, but when they arrive, Harry and Ron inexplicably cannot get through the secret entrance to Platform 9 ¾, so they decide to fly the Weasley's car to Hogwarts instead. Things get dangerous when Ron loses control of the car, and it falls from the sky into a Whomping Willow (a tree that attacks anyone who approaches it). Ron and Harry escape from the tree, but Ron's wand is broken in the process. The next day, Ron receives a Howler from his mother, Molly Weasley, threatening to send him home if he puts another toe out of line.

Lockhart turns out to be an incompetent teacher, more concerned with personal celebrity than teaching. On Halloween, Mrs. Norris, a cat belonging to the school caretaker's is found petrified. On a wall nearby appears a message: "The Chamber of Secrets has been opened. Enemies of the heir, beware." Harry, Ron, and their best friend Hermione Granger discover that one of Hogwarts' founders, Salazar Slytherin, secretly built the Chamber of Secrets, which is rumoured to contain a monster that only Slytherin's heir can directly control. Slytherin disapproved of wizards and witches with Muggle parents (muggleborns) being allowed to attend Hogwarts and supposedly built the Chamber so that one day his heir could purge the school of them.

In the novel, Dumbledore owns a pet bird known as a phoenix a famous mythological fire bird. In the novel, the tears of the bird contain healing properties.

Suspecting that Harry's nemesis, Draco Malfoy, is the heir of Slytherin, the trio spends a month making Polyjuice Potion, a brew that will allow them, for a period, to look like someone else. Their makeshift laboratory is in a bathroom haunted by the ghost of Moaning Myrtle.

During a game of Quidditch, Harry's arm is broken by a rogue Bludger, although he still catches the snitch to win the game. Lockhart volunteers to heal the broken bones but removes them instead. That night, as Harry lies mending in his hospital bed, Dobby appears and admits responsibility for the platform incident and the rogue Bludger, out of a desire to stop Harry from being able to attend Hogwarts. He begs Harry to leave Hogwarts, insisting that he is in danger, and lets slip that the Chamber of Secrets has been opened before. Soon after, a first-year student, Colin Creevey, is attacked and petrified.

During the first meeting of Lockhart's new dueling club, Harry duels with Draco, who casts a snake that tries to attack a student, Justin Finch-Fletchley. In his efforts to stop it, Harry unwittingly speaks Parseltongue. The sudden appearance of this ability—also possessed by Salazar Slytherin—shocks everyone, since it suggests that Harry might be Slytherin's heir. Harry comes under further suspicion when he stumbles upon the petrified bodies of Justin Finch-Fletchley and Nearly Headless Nick.

At Christmas, Harry and Ron use the finished Polyjuice Potion to disguise themselves as Draco's two friends Crabbe and Goyle. Hermione is unable to join them, having accidentally used cat hairs instead of human hairs in her sample of the potion, and subsequently turning into a human-cat hybrid when she drank it. Talking to Draco in the Slytherin common room, Harry and Ron discover that Draco is not the Heir of Slytherin and that the Chamber was last opened fifty years before.

After a few quiet months, Harry finds a diary in Myrtle's bathroom, which has flooded. He writes in the diary, which responds by displaying the name "Tom Riddle." Communicating with "Riddle" by writing in the diary, Harry learns that Hagrid was found to handle opening the Chamber of Secrets fifty years ago. Some time later, Harry's room is ransacked, and the diary taken. Hermione and a Ravenclaw girl, Penelope Clearwater, are petrified as well. Harry and Ron intend to question Hagrid, but before they can, he is accused of opening the Chamber of Secrets again and is taken to Azkaban prison. Before Hagrid is led away, he secretly instructs the boys to "follow the spiders" into the Forbidden Forest. There they encounter Aragog, a giant spider whom Hagrid had raised in secret during his days at Hogwarts, who tells them the monster who killed the girl 50 years before was not a spider, that the girl's body was found in a bathroom, and that Hagrid is innocent. The boys escape a colony of giant spiders, who are instructed by Aragog to eat them. They also realise that the girl Aragog referred to must have been Moaning Myrtle.

The novel reveals that the "monster" in the Chamber of Secrets is the legendary reptile known as the Basilisk.

Harry and Ron learn from a piece of paper Hermione was holding when she was attacked that the monster is a Basilisk, a giant snake that kills those who look it in the eye, although the petrified victims only ever saw it in a reflection or through a medium. They later discover the entrance to the Chamber in Myrtle's bathroom, which Harry opens by speaking Parseltongue. They have brought with them Lockhart, whom they have caught trying to run away from Hogwarts. He steals Ron's wand and attempts a memory charm on them, revealing that he is a fraud whose "great accomplishments" were stories he stole from other wizards whose memories he then erased. He admits that the memory charm is the only one that he can do right. As he attempts to erase their memories, Ron's broken wand reflects the spell back at Lockhart, knocking him down and erasing all of Lockhart's memory. Harry is forced to go on alone after the spell causes a cave-in.

Inside the chamber, Harry finds the unconscious body of Ron's sister Ginny, as well as the almost physical form of Riddle who reveals that Ginny had been communicating with him by writing in his diary, allowing him to possess her and have her set the Basilisk on the Muggleborns. Ginny had realised that the diary was not what it seemed and tried to dispose of it in Myrtle's bathroom, but stole it back when she saw Harry with it, afraid that her crimes would be revealed. Riddle then forced Ginny to enter the Chamber, to lure Harry down there, and, by possessing Ginny's soul, began to take physical form. Riddle reveals that his name, Tom Marvolo Riddle, is an anagram for I am Lord Voldemort and that he is Voldemort's past self.

Riddle then summons the Basilisk and orders it to attack Harry. Just when it seems Harry will be killed, Fawkes, Dumbledore's pet phoenix, appears and blinds the Basilisk. Fawkes carries the Sorting Hat, from which Harry draws a sword and kills the Basilisk, but one of its fangs pierces Harry's arm. Healed by Fawkes's healing tears, Harry stabs the diary with a Basilisk fang, defeating Riddle and saving Ginny. The two return with Ron and Lockhart to the school, where Ginny is reunited with her parents, and Harry and Ron are commended by Dumbledore. In the aftermath, Harry accuses the school governor, Lucius Malfoy (Draco's father), of putting the journal in Ginny's cauldron in the first place, and later tricks him into freeing Dobby. Malfoy is sacked as governor, the final exams are cancelled, and Lockhart resigns as a professor.

Rowling found it difficult to finish Harry Potter and the Chamber of Secrets because she was afraid it would not live up to the expectations raised by Harry Potter and the Philosopher's Stone (Harry Potter and the Sorcerer's Stone in the U.S.). After delivering the manuscript to Bloomsbury on schedule, she took it back for six weeks of revision.[2]

In early drafts of the book, the ghost Nearly Headless Nick sang a self-composed song explaining his condition and the circumstances of his death. This was cut as the book's editor did not care for the poem, which has been subsequently published as an extra on J. K. Rowling's official website.[3] The family background of Dean Thomas was removed because Rowling and her publishers considered it an "unnecessary digression", and she considered Neville Longbottom's own journey of discovery "more important to the central plot".[4]

Harry Potter and the Chamber of Secrets was published in the UK on 2 July 1998 and in the US on 2 June 1999.[5][6] It immediately took first place in UK best-seller lists, displacing popular authors such as John Grisham, Tom Clancy,[2] and Terry Pratchett,[7] and making Rowling the first author to win the British Book Awards Children's Book of the Year for two years in succession.[8] In June 1999, it went straight to the top of three US best-seller lists,[9] including The New York Times'.[10]

First edition printings had several errors, which were fixed in subsequent reprints.[11] Initially Dumbledore said that Voldemort was the last remaining ancestor of Salazar Slytherin, instead of his descendant.[11]Gilderoy Lockhart's book on werewolves is entitled Weekends with Werewolves at one point and Wanderings with Werewolves later in the book.[12]

"Harry Potter and the Chamber of Secrets" was met with near universal acclaim. In The Times, Deborah Loudon described Harry Potter and the Chamber of Secrets as a children's book that would be "re-read into adulthood" and highlighted its "strong plots, engaging characters, excellent jokes and a moral message which flows naturally from the story".[13] Fantasy author Charles de Lint agreed, and considered the second Harry Potter book as good as Harry Potter and the Philosopher's Stone, a rare achievement among series of books.[14] Thomas Wagner regarded the plot as very similar to that of the first book, based on searching for a secret hidden under the school. However, he enjoyed the parody of celebrities and their fans that centres round Gilderoy Lockhart, and approved of the book's handling of racism.[15] Tammy Nezol found the book more disturbing than its predecessor, particularly in the rash behaviour of Harry and his friends after Harry withholds information from Dumbledore, and in the human-like behaviour of the mandrakes used to make a potion that cures petrification. Nevertheless she considered the second story as enjoyable as the first.[16]

Mary Stuart thought the final conflict with Tom Riddle in the Chamber was almost as scary as in some of Stephen King's works, and perhaps too strong for young or timid children. She commented that "there are enough surprises and imaginative details thrown in as would normally fill five lesser books." Like other reviewers, she thought the book would give pleasure to both children and adult readers.[17] According to Philip Nel, the early reviews gave unalloyed praise while the later ones included some criticisms, although they still agreed that the book was outstanding.[18]

Writing after all seven books had been published, Graeme Davis regarded Harry Potter and the Chamber of Secrets as the weakest of the series, and agreed that the plot structure is much the same as in Harry Potter and the Philosopher's Stone. He described Fawkes's appearance to arm Harry and then to heal him as a deus ex machina: he said that the book does not explain how Fawkes knew where to find Harry; and Fawkes's timing had to be very precise, as arriving earlier would probably have prevented the battle with the basilisk, while arriving later would have been fatal to Harry and Ginny.[19]

Rowling's Harry Potter and the Chamber of Secrets was the recipient of several awards.[20] The American Library Association listed the novel among its 2000 Notable Children's Books,[21] as well as its Best Books for Young Adults.[22] In 1999, Booklist named Harry Potter and the Chamber of Secrets as one of its Editors' Choices,[23] and as one of its Top Ten Fantasy Novels for Youth.[20] The Cooperative Children's Book center made the novel a CCBC Choice of 2000 in the "Fiction for Children" category.[24] The novel also won Children's Book of the Year British Book Award,[25] and was shortlisted for the 1998 Guardian Children's Award and the 1998 Carnegie Award.[20]

Harry Potter and the Chamber of Secrets continues the examination of what makes a person who he or she is, which began in the first book. As well as maintaining that Harry's identity is shaped by his decisions rather than any aspect of his birth,[16][29]Harry Potter and the Chamber of Secrets provides contrasting characters who try to conceal their true personalities: as Tammy Nezol puts it, Gilderoy Lockhart "lacks any real identity" because he is nothing more than a charming liar.[16] Riddle also complicates Harry's struggle to understand himself by pointing out the similarities between the two: "both half-bloods, orphans raised by Muggles, probably the only two Parselmouths to come to Hogwarts since the great Slytherin."[30]

Opposition to class, death and its impacts, experiencing adolescence, sacrifice, love, friendship, loyalty, prejudice, and racism are constant themes of the series. In Harry Potter and the Chamber of Secrets Harry's consideration and respect for others extends to the lowly, non-human Dobby and the ghost Nearly Headless Nick.[31] According to Marguerite Krause, achievements in the novel depend more on ingenuity and hard work than on natural talents.[32]

Edward Duffy, an associate professor at Marquette University, says that one of the central characters of Chamber of Secrets is a book, Tom Riddle's enchanted diary, which takes control of Ginny Weasley – just as Riddle planned. Duffy suggests that Rowling intended this as a warning against passively consuming information from sources that have their own agendas.[33] Although Bronwyn Williams and Amy Zenger regard the diary as more like an instant messaging or chat room system, they agree about the dangers of relying too much on the written word, which can camouflage the author, and they highlight a comical example, Lockhart's self-promoting books.[34]

Immorality and the portrayal of authority as negative are significant themes in the novel. Marguerite Krause states that there are few absolute moral rules in Harry Potter's world, for example Harry prefers to tell the truth, but lies whenever he considers it necessary – very like his enemy Draco Malfoy.[32] At the end of Harry Potter and the Chamber of Secrets, Dumbledore retracts his promise to punish Harry, Ron, and Hermione if they break any more school rules – after Professor McGonagall estimates that they have broken over 100 – and lavishly rewards them for ending the threat from the Chamber of Secrets.[35] Krause further states that authority figures and political institutions receive little respect from Rowling.[32] William MacNeil of Griffith University, Queensland, Australia states that the Minister for Magic is presented as a mediocrity.[36] In his article "Harry Potter and the Secular City", Ken Jacobson suggests that the Ministry as a whole is portrayed as a tangle of bureaucratic empires, saying that "Ministry officials busy themselves with minutiae (e.g. standardising cauldron thicknesses) and coin politically correct euphemisms like 'non-magical community' (for Muggles) and 'memory modification' (for magical brainwashing)."[29]

This novel implies that it begins in 1992: the cake for Nearly-Headless Nick's 500th deathday party bears the words "Sir Nicholas De Mimsy Porpington died 31 October 1492".[37][38]

Chamber of Secrets has many links with the sixth book of the series, Harry Potter and the Half-Blood Prince. In fact, Half-Blood Prince was the working title of Chamber of Secrets and Rowling says she originally intended to present some "crucial pieces of information" in the second book, but ultimately felt that "this information's proper home was book six".[39] Some objects that play significant roles in Half-Blood Prince first appear in Chamber of Secrets: the Hand of Glory and the opal necklace that are on sale in Borgin and Burkes; a Vanishing Cabinet in Hogwarts that is damaged by Peeves the Poltergeist; and Tom Riddle's diary, which is later shown to be a Horcrux.[40] Additionally, these two novels are the ones with the most focus on Harry's relationship with Ginny Weasley.